Watch that twitch

How airport security identifies suspicious characters

WHEN in August last year Britain's security services uncovered an alleged plot to smuggle the liquid components of a bomb onto an aircraft at Heathrow, the world's busiest international airport almost ground to a halt as additional passenger checks were ordered. It was not just flights starting from Heathrow that were delayed or cancelled, but many incoming services too. In the following days British Airways alone cut more than 1,200 flights.

There seemed to be total confusion. Could mothers take baby milk on board? Should medicines be put into checked baggage? Had duty-free been banned? And what about people arriving on connecting services from airports where no such checks were being carried out? Rules appeared to change by the hour.

“That sort of confusion can cause passengers not to want to fly with us any more,” says Georgina Graham, IATA's head of security. She thinks the industry has begun to co-ordinate better, but wants more to be done. Rules still vary in different parts of the world, leaving passengers puzzled.

Intelligence to prevent attacks is part of what experts call a “layered” security approach. Other layers include checking identities, scanning people and their luggage and searching them at random. Another and increasingly important one is to see how they behave. “There are identifiers of people who have hostile intent that you can pick up,” says Kip Hawley, the head of America's Transportation Security Administration. “Our testing indicates an extraordinary high degree of success.” This is not the same as building profiles of possible suspects and looking out for those sorts of people. “It doesn't do any good to say, ‘this is what I think a terrorist looks like and I think I'm going to frisk him,'” he explains.

Security officials with the Israeli airline El Al already spend a long time questioning passengers in order to identify behavioural traits that mark them out as dangerous. But El Al is small and America's airports would grind to a halt if such time-consuming procedures were adopted everywhere. So the system that will emerge in America is likely to involve pre-screening of passengers right from the time they make their reservation.

Then, as they go through the different layers of security at the airport, some passengers will be asked questions by specially trained staff who are looking out for things like involuntary facial-muscle movements. A twitch is impossible to hide. “The more you try to avoid it, the more pronounced it becomes,” says Mr Hawley. Eventually, he thinks, the analysis and interpretation of passengers' behaviour will be aided by machines.

Machines used to scan luggage at airports are getting more powerful too. Instead of just alerting staff to suspicious images, newer scanners will be able to work out what they show. New biometric passports, which contain details such as finger prints and iris scans, will also improve identification. A company called Clear is operating a registered-traveller programme at a growing number of American airports. For an annual fee of $99.95 it will issue a biometric identity card to people who pass government background checks, entitling the holders to use fast lanes at security checkpoints.

But Mr Hawley insists that security measures should not rely solely on machines, however sophisticated, because threats change. It will take a combination of science and technology, he reckons, to reduce the hassle involved in passing through airports. That may make them safer, too: “You want it to be as smooth a process as possible, because then the abnormalities pop out.”